French astronomer, cartographer and mathematician. He was educated in Paris and obtained a degree in medicine in 1522. He spent time in prison in 1518 and again in 1524, probably for practicing judicial astrology. In 1531, he was appointed to the chair of mathematics at the Collége Royal, where he taught until his death. His most notable works are Arithmetica Pratica, printed in Paris in 1530 and reprinted in 1544, and the Protomathesis (in 15 books), published in 1532. He is also famous for trying to square the circle and was one of the first mathematicians to use decimal numbers. //